Compasses with releasable points

ABSTRACT

A needle point or pencil point is releasably fastened to a leg or branch of compasses in a receptacle slotted transversely to the plane of relative movement of the two branches or legs, the receptacle being clamped about the point by sliding a plastic sleeve longitudinally of the metallic receptacle toward a position of camming engagement between converging inner walls of the sleeve with converging outer walls of the receptacle, the angles of convergence being such that the sleeve is locked by static friction in the clamping position.

United States Patent 1 1 1111 3,787,380

Glombitza 5] Jan. 29, 1974 [54] COMPASSES WITH RELEASABLE POINTS 2,764,816 10/1956 Cesaris .3. 33/27 B Inventor: aus G omb tza Dall ngerstrasse 3,1 1 1,761 l 1/1963 McAllstcr 33/27 C 85 Numberg Germany Primary ExaminerLo uis R. Prince [73] Assignee: J. S. Staedtler, Numberg, Germany Assistant ExaminerCharles E. Phillips [22] Filed: Sept. 22 1971 Attorney, Agent, or FtrmKelman and Herman [21] Appl. No.: 182,700 57 ABSTRACT A needle point or pencil point is releasably fastened to [30] Foreign Application Priority Data a leg or branch of com'passes'ir'ia receptacle slotted 0m. 29, 1970 Germany P 20 53 253.0 transversely the Plane of relative movement; of the two branches or legs, the receptacle being clamped 52 US. Cl. 33/27 B, 33/149 H, 33/152 8 about the point y Sliding a Plastic sleeve longitudi- 51 1m. (:1 B43] 9/24 nally 0f the metallic receptacle toward a Position of 53 Field f Search 33 27 13 27 C, 49 H, 152 B camming engagement between converging inner walls v of the sleeve with converging outer walls of the recep- 5 References Cited tacle, the angles of convergence being such that the UNITED STATES PATENTS sleeve is locked by static friction in the clamping posi- 595,607 12 1297 Coykendall 33/27 B 2,367,584 1/1945 Hunt 33/27 B 1 Claim, 5 Drawing Figures PATENTEU T 3.787, 980

SHEET 1 BF 2 Fig.1

INVENTOR K/ us 6/0 bI f-Z'E AGENTS COMPASSES WITH RELEASABLE POINTS This invention relates to drafting instruments, and particularly to a chuck arrangement for compasses which clamps a needle point or a pencil point to a branch or leg of the compasses.

It is common practice to provide one branch of a pair of compasses with a slotted receptacle provided with external threads and an internally threaded sleeve which clamps the receptacle about a needlepoint or pencil point when threadedly shifted on the receptacle. While the known device, analogous to a chuck, has proven its worth over a long period, it is relatively costly to make when it is expected to meet requirements for high precision and good durability. I The primary object of the invention is the provision of a device for clamping a needle point or pencil point to a branch or leg of a pair'of compasses which meets all requirements for durability and precision, yet can be produced at much lower cost than the threaded chuck arrangement. I

With this object and others in view, as will hereinafter become apparent, the invention provides an elongated receptacle at. the free end of a compass branch with a longitudinal channel adapted to receive a point and with a slot transverse to the plane of relative movement of the two legs or branches of the pair of compasses. The slot intersects the channel, and the slot and channel are open longitudinally of the receptacle away from the portion of the branch which is pivotally connected to the other branch or leg.

The receptacle has a'pair of outer, longitudinal, opposite walls transverse to the plane of branch movement and converging. in the direction of receptacle elongation at a small acute angle. A sleeve member, which receives a longitudinal portion of the receptacle, has a pair of inner opposite walls transverse to the plane of branch movement and converging in the aforementioned direction of receptacle elongation at a small acute angle. The sleeve member engages the receptacle for sliding movement toward and away from a position of camming engagement of said pairs of walls under a pressure sufficient to deform said receptacle for narrowing said slot and thereby clamping a point received in the channel of the receptacle.

Other features, additional objects, and many of the attendant advantages of this invention will readily be appreciated as the invention is better understood by reference to the following detailed description of a preferred embodiment when considered in connection with the appended drawing in which:

FIG. 1 shows a pair of compasses of the invention in fragmentary front elevation, and partly in section;

FIG. 2 showselements of the apparatus of FIG. 1 in a corresponding view;

FIG. 3 is a side-elevational view of the device of FIG.

FIG. 4 shows another element of the apparatus of FIG. 1 infront elevation; and

FIG. 5 illustrates the device of FIG. 4 in side elevation.

Referring initially to FIG. 1, there is shown only as much of a pair of otherwise conventional compasses as is needed for an understanding of the invention. The portions of the two branches or legs 1,11 not seen in FIG. 1 are connected by a pivot, as is conventional, for relative angular movement of the illustrated free end portions, 2,12 in the plane of FIG. I toward and away from each other.

Each end portion is provided with a longitudinal channel 6,16, as is better seen in FIG. 2, which illustrates only the metallic elements of'the two branches. The cylindrical channels 6,16 are of different diameter so that the end portions 2,12 constitute receptacles for a needle point 8 and a pencil point 18 respectively, but the end portions 2,12 are practically identical in every other respect.

Slots 3,13 perpendicular to the plane of FIGS. 1 and 2 and thus to the plane of relative movement of the branches 1,11 intersect the channels 6,16. Stops 4,14 project from the bottom end of each receptacle 2,12 toward the other receptacle so to retain a plastic sleeve 5,15 on the receptacle. The sleeves 5,15 are longitudinally slidably on the receptacles 2,12, until, in their position farthest from the stops 4,14, they clamp the receptacles 2,12 tightly about the received points 8,18.

The receptacles 2,12 and the sleeves 5,15 are rectangular in each cross section perpendicular to the direction of elongation of the respective receptacle. Each receptacle has a pair of opposite outer walls 9,10; 19,20 perpendicular to the planes of FIGS.1 and 2 whose members converge toward the free end of the receptacle at a very small angle, smaller than 10. The sleeves 5,15 have corresponding walls not specifically shown, but parallel to the outer walls 21,22 as seen in F164, which converge at the same angle in the same direction.

When the sleeves 5,15 are moved away from the free ends of the receptacles 2,12, the inner sleeve walls cammingly engage the outer walls 9,10; 19,20 of the receptacles 2,12, and thereby narrow the slots 3,13 until the receptacles are clamped about the points 8,18.

The receptacles are made of nickel-plated brass or other metal customarily employed in drafting instruments, and the sleeves 5,15 consist of synthetic resin composition, polytetrafluoroethylene being preferred for this purpose because of its durability. Although the coefficient of static friction between the polymer and a polished nickel surface is very low, it is sufficient to prevent spontaneous movement of the sleeves 5,15 from their clamping positions if the clamping pressure is such as to resiliently deform the receptacle and to clamp the point received in the channel. The small angle of convergence of the walls 9,10; 19,20 and of the cooperating inner walls of the sleeves 5,15 is important for so securing the sleeves 5,15.

The walls 26,27 of each branch or leg 1,11 which connect the converging walls, and the corresponding inner walls 23,24 of each sleeve 5,15 are parallel to each other and do not participate in the clamping or camming cooperation of the sleeves and receptacles, as is evident from FIGS. 3 and 5.

the outer walls 10,20 of the receptacles 2,12 which face each other form the bottoms of respective elongated recesses in the receptacles which are bounded transversely by the stops- 4,14. The sleeves 5,15 are normally retainedin the recesses, and thereby prevented from falling from the associated receptacles.

Grooves 7,17 in the stems of the branches 1,11 near the receptacles 2,12 communicate with the channels 6,16 for convenient insertion of the points 8,18 as is best seen in FIGS. The faces of the sleeves 5,15 which extend in the direction of the plane of leg movement and longitudinally of the receptacles 2,12 are convexly arcuate in a plane drawn through the associated slot 3,13, as is evidentfrom FIG. 5, and carry ribs 25 parallel to the direction of leg movement and approximately perpendicular to the direction of leg elongation. The ribs 25 and the grooves alternating with them facilitate grasping of the sleeves 5,15.

The respective faces of the receptacles 2,12 which are directed toward each other are flush with corresponding faces of the main portions of the branches 1,11. The faces or walls 9,19 which are directed away from each other are angularly offset from the corresponding faces 1,11' on the main portions of the branches 1,11 by the acute angle, smaller than which provides the tapering configuration of each receptacle.

The receptacles of the invention are so shaped and dimensioned that they can be machined readily from bar stock on automatic machine tools in very few operations as will be evident from inspection of FlGS.2 and 3. The sleeves 5,15 are molded from plastic in an equally simple manner, the converging inner walls making the withdrawal of a core very simple.

The specific embodiment illustrated is preferred because of the features which permit it to be manufactured at low cost, but numerous modifications will readily suggest themselves. Except for minor chamfers on exposed edges and the recesses 7,17, all surfaces of the receptacles 2,12 are flat, and particularly the walls which engage inner walls of the sleeves 5,15 are planar.

If so desired, however, the walls of the receptacles which engage the sleeves may receive an arcuate configuration for cooperation with correspondingly contoured walls of the sleeves. The materials of construc-' tion chosen for their ability of being given the desired shapes may be replaced by others, and the use of allmetal or all-plastic construction, and of a combination of materials in which metal and plastic are interchanged in the illustrated apparatus are specifically contemplated.

While the receptacles 2,12 have been shown to be integrally attached to the legs or branches 1,11, they may be fastened releasably for quick replacement of the needle tip 8 by one of different shape, or for replacement of the pencil point 18 by a pen, as is conventional in itself.

It should be understood, therefore, that the foregoing disclosure relates only to a preferred embodiment, and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the appended claims.

What is claimed is: V

1. In a compass drafting instrument having two elongated leg members pivotally joined at one end for movement in a plane, and chuck members disposed near the opposite ends of said elongated leg members for securing a needle point within one leg member and a marking point within the second leg member, the improvement which comprises in combination:

a. each said chuck member comprising a receptacle disposed at a small acute angle of less than 10 relative to the axial line of its respective leg member, said receptacles being formed of a longitudinal channel of uniform cylindrical bore extending from the terminal end of its leg member to a groove on the outer side wall of the leg member;

b. longitudinal slots disposed axially along opposite front and rear walls and intersecting the receptacles transverse of the plane of the leg members and separating the lower part of each leg member into two portions, the inner portion of which is of diverging thickness toward the pivotal point, and the outer portion of which is of converging thickness toward the pivotal point, the angle of divergence of the inner leg portion being greater than the angle of convergence of the outer leg portion;

c. two sleeve members consisting essentially of synthetic resin composition having a coefficient of friction sufficient to prevent spontaneous movement with respect to said leg members, said sleeve members each disposed around one of said leg members in camming engagement with said portions for clamping an element in the receptacle by sliding movementtoward the said pivotal point; and

d. a retaining shoulder disposed near the terminal end of each leg member on the inner facing wall surface thereof for restricting movement of said sleeve members beyond the end of the leg members.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,787,980 Dated January 29,1974

Inventor) KLA US GLOMBII'ZA It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Change: claim 1 to read:

l. In a compass drafting instrument having two elongated leg members pivotally joined at one end for movement in a plane, and chuck members disposed .near the opposite ends of said elongated leg members for securing a needle point within one leg member and a marking point within the second leg member, the improvement which comprises in combination:

(a) each said chuck member comprising a. receptacle formed of a longitudinal channel of uniform cylindrical bore extending from the terminal end of its leg member to a groove on the outer side wall of the leg member:

(b) longitudinal slots disposed axially along opposite front and rear walls and intersecting the receptacles transverse of the plane of the leg members and separating the lower part of each leg member into two portions, the inner portion of which is of diverging thickness toward the pivotal point, and the outer portion of which is of converging thickness toward the pivotal point, the angle of divergence of the inner leg portion being greater than the angle of convergence of the outer leg portion; Y

(c) each receptacle having a pair of outer, longitudinal,

opposite walls transverse to said plane and converging at a small acute angle of less than 10 in the direction of elongation of said leg menbers away from the pivotally joined ends of said leg members: a Y

(d) two sleeve members consisting essentially of synthetic resin composition having a coefficient of friction suf- FORM PO-1050 (10-69) uscoMM-Dc 60376-P69 i U. 5 ('OV ERNMENT PRINT NG OFFICE 1969 0-566-334.

UNITED STATES PATENT OFFICE Page 2 CERTIFICATE OF CORRECTION Patent No. r 3,787,980 Dated January 29, 1974 Inventor(s) KLAUS GLOMBITZA It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected asshown below:

ficient to prevent spontaneous movement with respect to said leg members, said sleeve members each disposed around one, of said leg members in camming engagement with said portions for clamping an element in the receptacle lay-sliding movement toward the said pivotal point;

and

(e) a retaining shoulder disposed near the terminal end of each leg) member on the inner .facing wall surfa for restricting movement of said sleeve members beyond the end of the leg members.

Signed and sealed this 11th day of June 197b,.

(SEAL) Attest:

EDWARD FIJIETOHERJR. Attesting Officer 0; V MARSHALL 1mm Commissioner of Patents USCOMM-DC 60376-P69 w u.s. GOVERNMENT PRINTING OFFICE: is" 0-366-884.

F ORM PO-l 050 (10-69) ce thereof 

1. In a compass drafting instrument having two elongated leg members pivotally joined at one end for movement in a plane, and chuck members disposed near the opposite ends of said elongated leg members for securing a needle point within one leg member and a marking point within the second leg member, the improvement which comprises in combination: a. each said chuck member comprising a receptacle disposed at a small acute angle of less than 10* relative to the axial line of its respective leg member, said receptacles being formed of a longitudinal channel of uniform cylindrical bore extending from the terminal end of its leg member to a groove on the outer side wall of the leg member; b. longitudinal slots disposed axially along opposite front and rear walls and intersecting the receptacles transverse of the plane of the leg members and separating the lower part of each leg member into two portions, the inner portion of which is of diverging thickness toward the pivotal point, and the outer portion of which is of converging thickness toward the pivotal point, the angle of divergence of the inner leg portion being greater than the angle of convergence of the outer leg portion; c. two sleeve members consisting essentially of synthetic resin composition having a coefficient of friction sufficient to prevent spontaneous movement with respect to said leg members, said sleeve members each disposed around one of said leg members in camming engagement with said portions for clamping an element in the receptacle by slidiNg movement toward the said pivotal point; and d. a retaining shoulder disposed near the terminal end of each leg member on the inner facing wall surface thereof for restricting movement of said sleeve members beyond the end of the leg members. 